The present invention is based upon the discovery that a simple, efficient, open, partial conversion system for the production of liquid natural gas (LNG) can be provided if natural gas, taken directly from the well head or other source under high pressure and cleaned (if required), is immediately thereafter split into two high pressure flow portions. The first high pressure flow portion is the source of the liquid natural gas fraction, the vent remainder of the first flow portion constituting a cold saturated vapor used thereafter as a coolant for the system. The second high pressure flow portion is cooled and is used solely as a coolant for the system. The second flow portion and the remainder of the first flow portion are ultimately conducted to an appropriate receiver having a pressure lower than that of the well head or other source. Neither of the first and second flow portions is reduced in pressure to a level less than the pressure within the receiver.
Prior art workers have devised many types of partial conversion and total conversion systems for the production of liquid natural gas. This is exemplified in U.S. Pat. No. 3,735,600 wherein an open cycle is taught utilizing well head gas. In this system, however, once the well head gas has been purified, it is not immediately split into two flow portions. The arrangement of equipment components differs from that of the present invention, as do the steps performed in the reference system.
Other exemplary prior art natural gas liquification systems are taught, for example, in U.S. Pat. Nos. 3,818,714 and 4,970,867, both of which demonstrate the more complex prior art approaches.